1. Field of the Invention
The present invention relates to a mobile terminal, and more particularly to a dual-mode mobile terminal that supports both synchronous and asynchronous modes.
2. Description of the Related Art
The use of mobile terminals has been rapidly increasing around the world. Mobile communication systems, which provide communication services to the mobile terminals, can be mainly divided into a GSM mobile communication system that is primarily used in Europe and a CDMA mobile communication system that is primarily used in North America. The CDMA mobile communication system employs a synchronous data transmission mode and the GSM mobile communication system employs an asynchronous data transmission mode. The synchronous mode achieves synchronization between a transmitter and a receiver using a GPS satellite signal, whereas the asynchronous mode achieves the synchronization using a special chip or software.
In some areas, both the synchronous CDMA mobile communication system and the asynchronous GSM mobile communication system provide overlapping mobile communication services. In such areas where the CDMA and GSM mobile communication systems are used together, users need to have CDMA terminals if they wish to receive CDMA services or GSM terminals if they wish to receive GSM services. Dual-mode mobile terminals, which can access both the synchronous CDMA and asynchronous GSM mobile communication systems to receive communication services therefrom, are under development to meet this need.
The dual-mode mobile terminal generally operates in one of the synchronous and asynchronous communication modes, and switches between the synchronous and asynchronous communication modes according to user selection.
Another dual-mode mobile terminal, which can access both the synchronous CDMA and asynchronous GSM mobile communication systems and operate in the synchronous and asynchronous communication modes at the same time, is also under development.
Although dual mode terminals are known in the art, there has been suggested no method or technology for controlling calls in the dual-mode mobile terminals, which can operate in the synchronous and asynchronous communication modes simultaneously, when the terminal receives calls from both the CDMA and GSM mobile communication systems at the same time.